It's impossible to know whether your polygrapher will automatically assume that you're lying when you deny having ever used an illegal drug. However, it seems likely that any polygrapher would at least be skeptical regarding any such claim.

A truthful person's fear of the consequences of not being believed can indeed create a reaction to a relevant question and lead to a false positive outcome. It's not at all uncommon.

I suggest that you download The Lie Behind the Lie Detector. In Chapter 3 you'll find polygraph procedure explained in detail, and in Chapter 4 you'll find suggestions for reducing the risk of a false positive outcome.

I'm considering entering L.E.  Have a college degree, some good work experience, good credit, blah, blah, blah.  I was never into bars or clubs or the "crazy" lifestyle.  Pretty boring actually.   

Anyway, I have NEVER done illegal drugs.  But, anytime I tell anyone that, they think I am full of it.  (You must have tried this or that right?  )   

Will a polygrapher automatically assume I am lying when I say I have never done drugs?  I think that I might get a reaction to the question because I am thinking he won't believe me when I tell him "no" and then the reading will look deceptive even when I am truthful.  Any thoughts?